In Things Fall Apart, what is a Christian practice that was good for their people, but seen as an abomination by Ibo?

One example of a healthy or "good" practice of the
Christians was their willingness to go against traditional Ibo culture when it came to
traditions that appeared to be cruel or harmful.  They would rescue the twin babies from
the forbidden forest rather than allow them to starve and die there.  This is
particularly difficult because the practice seems to be so completely foreign and cruel,
yet was accepted among the Ibo people.

You might also make
the case that the Christians are trying to create a problem solving culture based on
discussion and diplomacy rather than one based almost entirely on conflict and
violence.  That could certainly be considered something that is "good" for people, if
you are trying to make that argument.